Environmental seal technology for spaced transparent armor

ABSTRACT

The present invention is embodied in environmental seal technology incorporated into a double-paned window, the environmental seal technology comprising an inner desiccant seal and a structural spacer. The subject invention solves the problem of moisture between the window panes by keeping the internal gap dry using a desiccant system. The invention also incorporates a durable structural spacer that will not rupture under normal military vehicle loads and environmental conditions. The spacer is bonded to the window panes using pressure-sensitive adhesives, thus allowing for easy manufacture.

BACKGROUND OF THE INVENTION

This invention relates generally to environmental seal technology forspaced transparent armor and, more particularly, to environmental sealtechnology incorporated into a double-paned window having an innerdesiccant seal combined with a structural spacer.

Spaced armor has been used for many years in opaque armor applications.The challenge for using it in transparent armor has been related to theenvironmental durability of the seal. The air between the glass laminateblocks must be kept clean and dry throughout the life of the armor.

In the insulated glass market, two or more panes of glass are used, withan air space defined between the panes. The primary purpose of the airspace is for insulation. The primary purpose for the air space intransparent armor is for improved ballistic protection, although the airspace also improves the product's insulation.

Several approaches have been used in the insulated glass industry tokeep the air between the glass panes clean and dry. None of theseapproaches appears to use a seal having sufficient strength forenvironmental and mechanical durability in military applications. In theinsulated glass industry, a seal of significant strength is notrequired. Thus, the primary seal is typically a low modulus elastomer.In a military vehicle application, the seal needs to be able towithstand substantial environmental and mechanical loading.

A few approaches that use an air gap have been tried in ballisticapplications. Many of these approaches have been designed for use in theperiscope market. An example is U.S. Pat. No. 4,149,778. This patentstates that the void between the spaced blocks is preferably filled withan inert gas such as dry nitrogen or may have a vacuum formed therein.Having a vacuum or inert gas in the gap, however, has been found to becumbersome and costly in larger military applications, such asdouble-paned windows for military vehicles.

Transparent armor for a passenger vehicle application is disclosed inU.S. Pat. No. 4,316,404. In this patent, a polycarbonate layer is bondedto a glass laminate using a double-sided tape, thus creating a thin airgap between the polycarbonate layer and the glass laminate. Thisapproach, however, fails to use a seal having sufficient strength forenvironmental and mechanical durability in military applications, anddoes not address the issue of moisture within the air gap.

It should thus be appreciated that there is a need for environmentalseal technology for spaced transparent armor that combines a strong,durable seal with a means for keeping the air between the glass laminateblocks clean and dry. The system should function without the need forinert gas or a vacuum in the gap between the glass laminate blocks. Thepresent invention fulfills this need and provides further relatedadvantages.

SUMMARY OF THE INVENTION

The present invention is embodied in a spaced transparent armorstructure comprising a desiccant system and a structural spacer. Thesubject invention solves the problem of moisture between the windowpanes of the spaced transparent armor structure by keeping the internalgap dry using the desiccant system. The invention also incorporates adurable structural spacer that will not rupture under normal militaryvehicle loads and environmental conditions. The spacer is bonded to thewindow laminates using pressure-sensitive adhesives, thus allowing foreasy manufacture.

In one embodiment, the spaced transparent armor structure comprises afirst transparent laminate configured as a pane having a first face, asecond face, and an edge; a second transparent laminate configured as apane having a first face, a second face, and an edge; a structuralspacer bonded to the second face of the first transparent laminate andto the first face of the second transparent laminate; and a desiccant.The first and second transparent laminates are spaced in a substantiallyparallel relationship so that an air gap is defined therebetween. Thedesiccant is positioned to absorb moisture trapped in the air gap.

In one embodiment, the desiccant is contained in an inner desiccant sealthat circumscribes the air gap and that extends between the second faceof the first transparent laminate and the first face of the secondtransparent laminate. The inner desiccant seal comprises a polymerbinder. The desiccant is supported in the polymer binder. The polymerbinder is selected from the group consisting of silicone foam, ethylenepropylene (EPM), ethylene propylene diene (EPDM) rubber,styrene-butadiene rubber (SBR), nitrile, and polyurethanes. The innerdesiccant seal comprises at least twenty percent desiccant.

In one embodiment, the structural spacer has an elastic modulus greaterthan 300 psi. The polymer binder has an elastic modulus greater than 200psi and less than the elastic modulus of the structural spacer. Thestructural spacer circumscribes the inner desiccant seal and comprises amaterial selected from the group consisting of polyurethanes, polymethylmethacrylate, and metals.

In one embodiment, the desiccant is embedded in the structural spacer.In another embodiment, the structural spacer is configured as a hollowtube. The desiccant is embedded within the hollow of the tube.

In one embodiment, the spaced transparent armor structure furthercomprises a film adhesive. The structural spacer is bonded to the secondface of the first transparent laminate and to the first face of thesecond transparent laminate by means of the film adhesive. The filmadhesive is a pressure-sensitive tape adhesive, such as acrylic foamtape.

In one embodiment, the spaced transparent armor structure furthercomprises a gasket bonded to the edge of the first transparent laminateand to the edge of the second transparent laminate by means of asealant. The sealant is selected from the group consisting of silylmodified polymer sealants, urethane sealants, polysulide sealants,silyl-terminated-polyether sealants, acrylic sealants, and siliconesealants. The gasket extends from the second face of the firsttransparent laminate to the second face of the second transparentlaminate.

In one embodiment, the spaced transparent armor structure furthercomprises a urethane backfill that circumscribes the structural spacerand that extends between the second face of the first transparentlaminate and the first face of the second transparent laminate. Theurethane backfill additionally extends at least partially between thestructural spacer and the second face of the first transparent laminate,and at least partially between the structural spacer and the first faceof the second transparent laminate. The urethane backfill furtherextends around the edge of the first transparent laminate and the edgeof the second transparent laminate.

In one embodiment, the spaced transparent armor structure furthercomprises a frame into which the first transparent laminate and thesecond transparent laminate are potted.

Other features and advantages of the invention should become apparentfrom the following description of the preferred embodiments, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a spaced transparent armorstructure, in accordance with an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a spaced transparent armorstructure having a desiccant-filled structural spacer, in accordancewith an embodiment of the present invention.

FIG. 3 is a partial cross-sectional view of a spaced transparent armorstructure having a desiccant-filled structural spacer and a urethanebackfill, in accordance with an embodiment of the present invention.

FIG. 4 is a partial cross-sectional view of a spaced transparent armorstructure having a solid structural spacer and inner desiccant seal, inaccordance with an embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of a spaced transparent armorstructure having a solid structural spacer, inner desiccant seal, andurethane backfill, in accordance with an embodiment of the presentinvention.

FIG. 6 is a partial cross-sectional view of a spaced transparent armorstructure having a pair of transparent laminates, a structural spacer,and a urethane backfill that extends partially between the structuralspacer and the transparent laminates, in accordance with an embodimentof the present invention.

FIG. 7 is a partial cross-sectional view of a spaced transparent armorstructure having a pair of transparent laminates, a structural spacer,and a urethane backfill that extends around the edges of bothtransparent laminates as well as partially between the structural spacerand the transparent laminates, in accordance with an embodiment of thepresent invention.

FIG. 8 is a partial cross-sectional view of a spaced transparent armorstructure having an elastomer gasket, in accordance with an embodimentof the present invention.

FIG. 9 is a partial cross-sectional view of a spaced transparent armorstructure 180 having a pair of transparent laminates and a metal frameinto which the transparent laminates are potted, in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, there is shown a cross-sectional view of aspaced transparent armor structure 10, in accordance with an embodimentof the present invention. The spaced transparent armor structurecomprises a pair of transparent laminates 12, each transparent laminateconfigured as a substantially rectangular pane having an outer face 14,an inner face 16, and an edge 18. The transparent laminates may compriseglass and/or other transparent or translucent materials.

The inner faces 16 of the transparent laminates 12 are spaced in asubstantially parallel relationship so that an air gap 20 is definedtherebetween. The air gap is configured as a substantially rectangularspace, the edges of which are bounded by an inner desiccant seal 22 thatextends between the inner faces of the transparent laminates. AlthoughFIG. 1 shows the spaced transparent armor structure 10 as having twotransparent laminates, the present invention encompasses spacedtransparent armor structures having more than two transparent laminates.

The inner desiccant seal 22 is a composition of a desiccant supported ina polymer binder. The desiccant absorbs moisture trapped between theinner faces 16 of the transparent laminates 12. An advantage to thisapproach is that the spaced transparent armor structure 10 can beassembled without the need for an inert gas or vacuum, which gives thisapproach a cost advantage over other forms of fabrication.

The desiccant material can be embedded within one of a number ofelastomers to create a seal. For example, Super Spacer® Triseal™ fromEdgetech I.G. of Cambridge, Ohio, is a desiccant embedded in siliconefoam. Other suitable elastomers include ethylene propylene (EPM),ethylene propylene diene (EPDM) rubber, styrene-butadiene rubber (SBR),nitrile, chloroprene, Epichlorohydrin, polyacrylic, fluorosilicone,perfluroelastomers, polyether block polyamides, chlorosulfonatedpolyethylene, ethylene-vinyl acetate, thermoplastic elastomers,thermoplastic vulcanizates, thermoplastic polyurethane (TPU),thermoplastic olefins, and polysulfide rubber. The desiccant couldadditionally or alternatively be embedded within one of a number ofplastics, including polypropylene, polystyrene,acrylonitrile/butadiene/styrene (ABS), polyethylene terephthalate,polybutylene terephthalate, polyester alloys, nylons, poly(vinylchloride), polyurethanes, polycarbonate, polyethylene, polymethylmethacrylate, polytetrafluoroethylene, polyetheretherketone,polyetherimide, and phenolics. In one embodiment, the desiccant isembedded within a polymer having an elastic modulus greater than 200 psiand less than the modulus of the structural spacer (described below).

Desiccants that may be used in the present invention include activatedalumina, aerogel, benzophenone, bentonite clay, calcium chloride,calcium hydride, calcium sulfate, copper(II) sulfate, lithium chloride,lithium hydride, lithium bromide, magnesium, magnesium sulfate,magnesium perchlorate, sodium potassium alloy, phosphorus pentoxide,potassium carbonate, silica gel, sodium chlorate, sodium hydroxide,sodium sulfate, sodium benzophenone, and molecular sieves. In oneembodiment, the inner desiccant seal 22 comprises twenty percentdesiccant.

The spacing between the pair of transparent laminates 12 is maintainedby a structural spacer 24, which surrounds the inner desiccant seal 22and extends between the inner faces 16 of the transparent laminates. Thestructural spacer may comprise hard elastomers, composites, plastics,metals, and/or metal alloys. Suitable hard elastomers include ethylenepropylene monomer (EPM) rubber, ethylene propylene diene monomer (EPDM)rubber, styrene-butadiene (SBR), nitrile, chloroprene, Epichlorohydrin,polyacrylic, fluorosilicone, perfluroelastomers, polyether blockpolyamides, chlorosulfonated polyethylene, ethylene-vinyl acetate,thermoplastic elastomers, thermoplastic vulcanizates, thermoplasticpolyurethane (TPU), thermoplastic olefins, and polysulfide rubber.Suitable plastics include polypropylene, polystyrene,acrylonitrile/butadiene/styrene (ABS), polyethylene terephthalate,polybutylene terephthalate, polyester alloys, nylons, poly(vinylchloride), polyurethanes, polycarbonate, polyethylene, polymethylmethacrylate, polytetrafluoroethylene, polyetheretherketone,polyetherimide, and phenolics. Suitable metals and metal alloys includeiron, aluminum, copper, stainless steel, nickel, magnesium, zinc, andtitanium alloys. In one embodiment, the material comprising thestructural spacer has an elastic modulus greater than 300 psi.

Composites, including fiber reinforced composites, would be suitable forlightweight structural spacers. Suitable fiber reinforced composites maycomprise glass and/or carbon fibers, and matrices of epoxy, vinyl ester,polyester, phenolics, and/or polyimides. The structural spacer 24 alsoacts as a moisture barrier. Low permeability materials such aspolyurethanes, polymethyl methacrylate, and metals are also suitable forthe structural spacer.

In one embodiment, the structural spacer 24 is an extrusion of any ofthe previously stated materials. The extrusion may comprise polymer,composite, elastomer, plastic, and/or metallic extrusions. A desiccantmay be embedded within the extrusion. The structural spacer may have asolid cross-section or a hollow cross-section (hollow tube).

The structural spacer 24 is bonded to the inner faces 16 of thetransparent laminates 12 using a film adhesive, such aspressure-sensitive tape adhesive 26. Bonding with a pressure-sensitivetape adhesive allows for a much quicker and cleaner application methodthan a paste adhesive, and the cleanliness of the pressure-sensitivetape adhesive eliminates a source of potential messes in the air gap 20.A pressure-sensitive tape adhesive also has near immediate bondstrength, thus allowing for a quicker and easier application method.Furthermore, a pressure-sensitive tape adhesive can act as an additionalmoisture barrier. Suitable pressure-sensitive tape adhesives includeacrylic foam tapes, such as HyperJoint H8000 series (Nitto DenkoCorporation of Osaka, Japan), HyperJoint H9000 series (Nitto DenkoCorporation of Osaka, Japan) and Very High Bonding (VHB) tapes (3MCompany of Maplewood, Minn.). Other suitable film adhesives includeurethane, polyvinyl butyral (PVB), and epoxies. Although FIG. 1 showsthe use of a pressure-sensitive tape adhesive, the present inventionencompasses the use of other adhesives, including paste adhesives.

In one embodiment, a pressure-sensitive tape adhesive is not used, andthe structural spacer 24 is instead bonded to the inner faces 16 of thetransparent laminates 12 using a hot-melt adhesive. A hot-melt adhesiveallows for good control of adhesive placement, without the need forcleanup. Suitable hot-melt adhesives include Jet-melt™ Adhesive by 3MCompany of Maplewood, Minn.

To mount the transparent laminates 12 into a vehicle, the transparentlaminates can be potted into a frame, or a gasket 28 can be bonded tothe edges 18 of the transparent laminates and the structural spacer 24using a sealant, such as pressure-sensitive tape adhesive 26 and/orurethane adhesive 30. Either of these methods adds another sealant layerbetween the air gap 20 and the outside environment, and thus furtherimproves the environmental and mechanical durability of the spacedtransparent armor structure 10. Suitable sealants include silyl modifiedpolymer sealants, urethane sealants, polysulfide sealants,silyl-terminated-polyether sealants, acrylic sealants, and siliconesealants.

The gasket 28 is configured to extend around the edges 18 of bothtransparent laminates 12, extending from the outer face 14 of onetransparent laminate to the outer face of the other transparentlaminate. In one embodiment, pressure-sensitive tape adhesive 26 is usedto bond the gasket to the outer faces of the transparent laminates,while urethane adhesive 30 is used to bond the gasket to the edges 18 ofthe transparent laminates and the structural spacer 24. The spacedtransparent armor structure 10 may comprise a single gasket or aplurality of gaskets as needed to mount the transparent laminates into avehicle.

In some embodiments, a desiccant is embedded within the structuralspacer extrusion, so that a separate inner desiccant seal isunnecessary. With reference to FIG. 2, there is shown a partialcross-sectional view of a spaced transparent armor structure 40 having apair of transparent laminates 42, an air gap 44 defined therebetween,and a desiccant-filled structural spacer 46 bonded to the transparentlaminates using pressure-sensitive tape adhesive 48, in accordance withan embodiment of the present invention. With reference to FIG. 3, thereis shown a partial cross-sectional view of a spaced transparent armorstructure 60 having a pair of transparent laminates 62, an air gap 64defined therebetween, a desiccant-filled structural spacer 66 bonded tothe transparent laminates using pressure-sensitive tape adhesive 68, anda urethane backfill 70, in accordance with an embodiment of the presentinvention. The urethane backfill 70 surrounds the outer perimeter of thedesiccant-filled structural spacer 66 and extends between thetransparent laminates 62 to provide additional sealing for the air gap64.

In other embodiments, a separate inner desiccant seal is used. Withreference to FIG. 4, there is shown a partial cross-sectional view of aspaced transparent armor structure 80 having a pair of transparentlaminates 82, an air gap 84 defined therebetween, a solid structuralspacer 86 bonded to the transparent laminates using pressure-sensitivetape adhesive 88, and an inner desiccant seal 90 bonded to the solidstructural spacer using pressure-sensitive tape adhesive, in accordancewith an embodiment of the present invention. Wither reference to FIG. 5,there is shown a partial cross-sectional view of a spaced transparentarmor structure 100 having a pair of transparent laminates 102, an airgap 104 defined therebetween, a solid structural spacer 106 bonded tothe transparent laminates using pressure-sensitive tape adhesive 108,and an inner desiccant seal 110 bonded to the solid structural spacerusing pressure-sensitive tape adhesive, and a urethane backfill 112, inaccordance with an embodiment of the present invention. The urethanebackfill 112 surrounds the outer perimeter of the solid structuralspacer 106 and extends between the transparent laminates 102 to provideadditional sealing for the air gap 104.

In some embodiments, the urethane backfill extends partially between thestructural spacer and the transparent laminates. With reference to FIG.6, there is shown a partial cross-sectional view of a spaced transparentarmor structure 120 having a pair of transparent laminates 122, an airgap 124 defined therebetween, a structural spacer 126 bonded to thetransparent laminates using pressure-sensitive tape adhesive 128, aninner desiccant seal 130 bonded to the structural spacer usingpressure-sensitive tape adhesive, and a urethane backfill 132 thatextends partially between the structural spacer and the transparentlaminates, in accordance with an embodiment of the present invention.Wither reference to FIG. 7, there is shown a partial cross-sectionalview of a spaced transparent armor structure 140 having a pair oftransparent laminates 142, an air gap 144 defined therebetween, astructural spacer 146 bonded to the transparent laminates usingpressure-sensitive tape adhesive 148, an inner desiccant seal 150 bondedto the structural spacer using pressure-sensitive tape adhesive, and aurethane backfill 152 that extends around the edges of both transparentlaminates as well as partially between the structural spacer and thetransparent laminates, in accordance with an embodiment of the presentinvention.

As noted above, the transparent laminates can be potted into a frame, ora gasket can be bonded to the edges of the transparent laminates and thestructural spacer. With reference to FIG. 8, there is shown a partialcross-sectional view of a spaced transparent armor structure 160 havinga pair of transparent laminates 162, an air gap 164 definedtherebetween, a structural spacer 166 bonded to the transparentlaminates using pressure-sensitive tape adhesive 168, an inner desiccantseal 170 bonded to the structural spacer using pressure-sensitive tapeadhesive, and an elastomer gasket 172 configured to extend around theedges of both transparent laminates and bonded thereto with a urethaneadhesive 174, in accordance with an embodiment of the present invention.With reference to FIG. 9, there is shown a partial cross-sectional viewof a spaced transparent armor structure 180 having a pair of transparentlaminates 182, an air gap 184 defined therebetween, a structural spacer186 bonded to the transparent laminates using pressure-sensitive tapeadhesive 188, an inner desiccant seal 190 bonded to the structuralspacer using pressure-sensitive tape adhesive, and a metal frame 192into which the transparent laminates are potted using a urethaneadhesive 194, in accordance with an embodiment of the present invention.

It should be appreciated from the foregoing disclosure that the presentinvention provides environmental seal technology for spaced transparentarmor that combines a strong, durable seal with a means for keeping theair between the glass laminate blocks clean and dry, the sealfunctioning without the need for inert gas or a vacuum in the gapbetween the glass laminate blocks.

Although the invention has been disclosed with reference only to thepresently preferred embodiments, those of ordinary skill in the art willappreciate that various modifications can be made without departing fromthe invention. Accordingly, the invention is defined only by thefollowing claims.

1. A spaced transparent armor structure comprising: a first transparentlaminate configured as a pane having a first face, a second face, and anedge; a second transparent laminate configured as a pane having a firstface, a second face, and an edge; a structural spacer bonded to thesecond face of the first transparent laminate and to the first face ofthe second transparent laminate; and a desiccant; wherein the structuralspacer has an elastic modulus greater than 300 psi; wherein the firstand second transparent laminates are spaced in a substantially parallelrelationship so that an air gap is defined therebetween; and wherein thedesiccant is positioned to absorb moisture trapped in the air gap. 2.The spaced transparent armor structure of claim 1, wherein the desiccantis contained in an inner desiccant seal that circumscribes the air gapand that extends between the second face of the first transparentlaminate and the first face of the second transparent laminate.
 3. Thespaced transparent armor structure of claim 2, wherein: the innerdesiccant seal comprises a polymer binder; and the desiccant issupported in the polymer binder.
 4. The spaced transparent armorstructure of claim 3, wherein the polymer binder is selected from thegroup consisting of silicone foam, ethylene propylene (EPM), ethylenepropylene diene (EPDM) rubber, styrene-butadiene rubber (SBR), nitrile,and polyurethanes.
 5. The spaced transparent armor structure of claim 4,wherein the polymer binder is silicone foam.
 6. The spaced transparentarmor structure of claim 1, wherein the polymer binder has an elasticmodulus greater than 200 psi and less than the elastic modulus of thestructural spacer.
 7. The spaced transparent armor structure of claim 2,wherein the inner desiccant seal comprises at least twenty percentdesiccant.
 8. The spaced transparent armor structure of claim 2, whereinthe structural spacer circumscribes the inner desiccant seal.
 9. Thespaced transparent armor structure of claim 1, wherein the structuralspacer comprises a material selected from the group consisting ofpolyurethanes, polymethyl methacrylate, and metals.
 10. The spacedtransparent armor structure of claim 1, wherein the desiccant isembedded in the structural spacer.
 11. The spaced transparent an norstructure of claim 1, wherein: the structural spacer is configured as ahollow tube; and the desiccant is embedded within the hollow of thetube.
 12. The spaced transparent armor structure of claim 1, furthercomprising a film adhesive, and wherein the structural spacer is bondedto the second face of the first transparent laminate and to the firstface of the second transparent laminate by means of the film adhesive.13. The spaced transparent armor structure of claim 12, wherein the filmadhesive is a pressure-sensitive tape adhesive.
 14. The spacedtransparent armor structure of claim 13, wherein the pressure-sensitivetape adhesive is an acrylic foam tape.
 15. The spaced transparent armorstructure of claim 1, further comprising a gasket bonded to the edge ofthe first transparent laminate and to the edge of the second transparentlaminate.
 16. The spaced transparent armor structure of claim 15,further comprising a sealant, and wherein the gasket is bonded to theedge of the first transparent laminate and to the edge of the secondtransparent laminate by means of the sealant.
 17. The spaced transparentarmor structure of claim 16, wherein the sealant is selected from thegroup consisting of silyl modified polymer sealants, urethane sealants,polysulide sealants, silyl-terminated-polyether sealants, acrylicsealants, and silicone sealants.
 18. The spaced transparent armorstructure of claim 17, wherein the sealant is a urethane sealant. 19.The spaced transparent armor structure of claim 15, wherein the gasketextends from the second face of the first transparent laminate to thesecond face of the second transparent laminate.
 20. The spacedtransparent armor structure of claim 1, further comprising a urethanebackfill that circumscribes the structural spacer and that extendsbetween the second face of the first transparent laminate and the firstface of the second transparent laminate.
 21. The spaced transparentarmor structure of claim 20, wherein the urethane backfill furtherextends at least partially between the structural spacer and the secondface of the first transparent laminate, and at least partially betweenthe structural spacer and the first face of the second transparentlaminate.
 22. The spaced transparent armor structure of claim 20,wherein the urethane backfill further extends around the edge of thefirst transparent laminate and the edge of the second transparentlaminate.
 23. The spaced transparent armor structure of claim 1, furthercomprising a frame into which the first transparent laminate and thesecond transparent laminate are potted.